set1 = {1,2,3}
set2 = {3,4,5}
set.update(set2)
set3 = set1 | set2
print("set3:",set3)#合并两个序列的元素

my_set = {1,2,3,4,5}
my_set.clear()
print("clear:",my_set)#清除所有元素

my_set = {1,2,3,4,5}
my_set.discard(3)
print("discard:",my_set)#删除元素3